1. Field of the Invention
The present invention relates to a timing controller and a liquid crystal display (LCD) device using the same, and more particularly, a timing controller for receiving RGB data to output WRGB data, a driving method thereof, and an LCD device using the same.
2. Discussion of the Related Art
With the advancement of various portable electronic devices such as mobile phones, personal digital assistants (PDAs), and notebook computers, the demand for Flat Panel Display (FPD) devices applicable to the portable electronic devices are increasing.
LCD devices, plasma display panels (PDPs), field emission display (FED) devices, and light emitting display devices are actively researched as FPD devices.
In such FPD devices, LCD devices are devices that display an image using the optical anisotropy of liquid crystal. Since the LCD devices have a thin thickness, a small size, and low power consumption and realize a high-quality, the LCD devices are widely used.
FIG. 1 is a timing chart for transferring RGB data from an embedded point to point interface (EPI) transmitter of a timing controller, applied to a related art LCD device, to a source driver IC. FIG. 2 is a timing chart for transferring WRGB data from the EPI transmitter of the timing controller, applied to the related art LCD device, to the source driver IC.
The related art LCD device includes a timing controller, a source driver IC, a gate diver IC, and a panel.
Generally, the panel of the related art LCD device includes a plurality of red (R) sub-pixels, green (G) sub-pixels, and blue (B) sub-pixels for realizing colors. To this end, input RGB data are inputted from an external system (for example, a television set) to the timing controller of the related art LCD device. In this case, the timing controller aligns input RGB data according to a pixel structure of the panel, and outputs the aligned RGB data to the source driver IC. The source driver IC converts digital WRGB data, received from the timing controller, into analog WRGB signals and outputs the analog WRGB signals to the panel.
An LCD device, having a WRGB pixel structure that includes both RGB sub-pixels having three primary colors and a white (W) sub-pixel transmitting white light, is recently developed for enhancing luminance of LCD devices. A timing controller of an LCD device having a WRGB pixel structure converts input RGB data, inputted from an external system, into WRGB data and outputs the WRGB data to the source driver IC. The source driver IC converts the digital WRGB data, received from the timing controller, into analog WRGB image signals and outputs the analog WRGB image signals to the panel.
In the two cases, the converted WRGB data from the timing controller are transferred to the source driver IC through one of various interfaces such as a mini-low voltage differential signaling (LVDS) interface and an EPI. Recently, the EPI is widely used as interface between the timing controller and the source driver IC.
FIG. 1 is a timing chart showing a timing in which when the timing controller receives the input RGB data and transfers the RGB data to the source driver IC, the EPI transmitter of the timing controller using the EPI scheme transfers the RGB data to the source driver IC.
When each of R, G, and B data composing the RGB data is composed of 10 bits, the EPI transmitter transfers 30-bit parallel data to the source driver IC by 34 bits according to EPI protocol. To provide an additional description, the EPI transmitter transfers 34-bit RGB data, in which 4 dummy bits have been added to the 30-bit RGB data, to the source driver IC.
In this case, as expressed in the following Equation (1), the maximum data transfer rate of the EPI transmitter is 1.156 Gbps. When the maximum frequency of a data clock is 85 MHz, the RGB data are composed of 34 bits, the RGB data are transferred to the source driver IC through four ports, and the number of source driver ICs (EPI ports) is 10, the maximum data transfer rate is 1.156 Gbps.Data Rate Max=85 MHz(Data Freq Max)×4(Port Number)/10(EPI Port)×34(Data Unit)=1.156 Gbps  (1)
The maximum data transfer rate is within a range of 1.6 Gbps that is the maximum data transfer rate between the EPI transmitter and the source driver IC. Therefore, the RGB data are normally transferred to the source driver IC.
FIG. 2 is a timing chart showing a timing in which when the timing controller receives the input RGB data, converts the RGB data into WRGB data, and transfers the WRGB data to the source driver IC, the EPI transmitter of the timing controller using the EPI scheme transfers the WRGB data to the source driver IC.
When each of R, G, and B data composing the RGB data is composed of 10 bits, the timing controller converts the 30-bit RGB data into 40-bit WRGB data, and the EPI transmitter segments 40-bit parallel data in units of 20 bits and transfers the segmented data to the source driver IC by 20 bits according to the EPI protocol. To provide an additional description, the EPI transmitter segments 40-bit parallel data in units of 20 bits and transfers 24-bit WRGB data including dummy bits to the source driver IC.
In this case, as expressed in the following Equation (2), the maximum data transfer rate of the EPI transmitter is 1.632 Gbps. When the maximum frequency of the data clock is 85 MHz, the WRGB data are composed of 24 bits, the RGB data are transferred to the source driver IC through four ports, there are two transfer paths, and the number of source driver ICs (EPI ports) is 10, the maximum data transfer rate is 1.632 Gbps.Data Rate Max=85 MHz(Data Freq Max)×[4(Port Number)×2(Pixel Split)]/10(EPI Port)×24(Data Unit)=1.632 Gbps  (2)
The maximum data transfer rate exceeds a range of 1.6 Gbps that is the maximum data transfer rate between the EPI transmitter and the source driver IC. Therefore, the WRGB data are not normally transferred to the source driver IC.
Therefore, in an LCD device using WRGB data, an input data clock is limited. That is, the LCD device using WRGB data uses a data clock range different from that of an LCD device using RGB data.
To transfer the WRGB data, the EPI transmitter and the source driver IC are driven at a speed higher than that of the LCD device using RGB data. However, as described above, since the maximum data transfer rate necessary for transferring WRGB data exceeds the maximum data transfer rate between the EPI transmitter and the source driver IC, it is substantially difficult to transfer WRGB data.
Moreover, since a data format (34 bits) for transferring RGB data differs from a data format (24 bits) for transferring WRGB data, it is impossible to identically apply the EPI transmitter and the source driver IC to both the LCD device using RGB data and the LCD device using WRGB data.
Moreover, when the EPI transmitter and source driver IC for transferring RGB data and the EPI transmitter and the source driver IC for transferring WRGB data are designed and manufactured separately, the manufacturing cost of the LCD device increases inevitably.
Moreover, as illustrated in FIG. 2, when 24-bit WRGB data are transferred, jitters severely occur between a first transfer unit and a last transfer unit.
The above-described drawbacks occur in all FPD devices using a timing controller, a source driver IC, and an EPI, in addition to LCD devices.